To gain access to the internet, a client (user) will typically login into an Internet Service Provider (ISP) via a telephone or ISDN modem. This connection is typically a medium data rate (i.e., 9.6 to 28.8 kbps), symmetrical connection. However, the client is typically searching for information, which leads to asymmetric communications. For example, a client (user) requesting a file download will send a small upstream request (e.g., 200 bytes) but receive a large file (e.g. 200 kbytes) in return from the server. In these types of connection the downstream channel (i.e., return link) is the bottleneck.
The typical volume of downstream data to upstream data ratio is from 10:1 to 20:1. Currently, asymmetrical channel services are being deployed (e.g., satellite broadcast, cable modems, ADSL, etc.) to take advantage of this ratio and reduce this downstream bottleneck. These services typically increase the downstream channel capacity by using a media with wider bandwidth (e.g., co-axial cable), and maintain or allocate a smaller bandwidth connection for the upstream user request channel. In some cases (such as satellite broadcast), an upstream channel path, independent of the downstream channel path, is utilized.
The Internet is a packet switch network, where the defacto protocol standard is TCP/IP. The Internet Protocol (IP) provides the basic addressing scheme for internet routing (where the information goes). Transmission Control Protocol (TCP) is very robust protocol designed for error-free bulk data transfer and error detection and correction. On top of TCP/IP, an additional serial interface, protocol (e.g., PPP or SLIP) is used for connection with an ISP. From the standpoint of upstream channel efficiency, a typical internet request has a high degree of packet overhead to accommodate the layers of protocol, the error correction, and the data coding scheme.
Browsing on the World Wide Web (WWW) (one of the most popular activities on the internet) also leads to inefficient use of the upstream channel. This browsing is based on the HyperText Transfer Protocol (HTTP). Typically, a user sends an HTTP request for a Web Page to a particular server on the internet and the server responds with requested information. This transaction takes several phases (i.e., Connect, Request, Response, Close) to complete. In addition, the requested information from the server is most commonly an HTTP file which references graphical images, audio files, and/or additional text. The browser will then automatically request the additional information (unless the user has manually selected to filter out certain high bandwidth file requests from being made). It is not uncommon for an initial request of a web page to trigger 20 more requests which are required to complete the transaction and build the image seen through the browser.